The group with Mazia is continuing the analysis of mitosis by techniques which separate the mitotic apparatus into a "nuclear mitotic apparatus" and a "cytoplasmic mitotic apparatus". The former depends on techniques which induce complete chromosome cycles in the sea urchin egg in the absence of centrioles; the latter is investigated by techniques which induce the production of numerous centrioles in unfertilized eggs. The respective contributions of nucleus and centrioles to the structure of the mitotic apparatus, the generation of centrioles and the interactions between chromosomes and poles will be assessed by experiments in vivo, by the electron microscopy and by experiments in vitro using microtubule-assembly systems. Strohman's group continues work on identification of specific biochemical processes underlying muscle fiber differentiation and fiber maturation and growth under conditions of muscle contraction and relaxation. The technical advances made now permit analysis of single culture dishes for (a) specific protein synthesis rates, (b) turnover rates for specific proteins, (c) presence of specific mRNA for a particular polypeptide. Thus the processes of development and growth of muscle can be fully explored in cell culture at the biochemical level. In Wilt's laboratory the stability of messenger RNA (mRNA) will be studied, especially the role of polyadenylation. The stability of histone mRNA, both non-adenylated and polyadenylation will be characterized. The stability of newly synthesized histone mRNA and histone mRNA synthesized and stored ssnthesized and stored during oogenesis will be compared. BIBLIOGRAPHIC REFERENCES: Huang, B. & D. Mazia 1975. Microtubules and filaments in ciliate contractility. In Molecules and Cell Movement, ed. S. Inoue & Stephens; Raven Press, New York. pp. 389-409. Schatten G. & D. Mazia 1976. The penetration of the spermatozoon through the sea urchin egg surface at fertilization: observations from the outside on whole eggs and from the inside on isolated surfaces. Exptl. Cell Res. 98:325-337.